There are disadvantages associated with all known massaging breast pump inserts and shields.
The breast pump insert described in EP0727234 (Avent Limited) has recessed petals which rest against the breast and then move away from the breast when suction is applied due to the fact that the vacuum is directed to the space between the massaging insert and the rigid support horn. It is doubtful if the movement away from the breast actually provides any massaging effect.
U.S. Pat. No. 7,396,339 (The First Years Inc.) also describes a breast pump insert with recessed massaging petals, comprising regions within the massaging insert with thinned walls. However, the suction is directed via channels in the insert to the thinned regions in the space between the insert and the breast. As such, when suction is applied from the breast pump, the thinned regions move towards the breast and apply a massaging pressure. This could provide useful massage, but relies on the channels in the wall of the insert to direct suction to the recesses. However, the channels are small and will easily be blocked by the user's own breast.
Alternatively, US2004024352 (Playtex) has a massaging insert with a membrane, which again applies positive massaging force to the breast, but which utilises a build-up of pressure in the cavity between the massaging insert and the supporting horn. The breast pump described in US2004024352 either provides for no suction to the breast, which would otherwise encourage milk expression in the manner of most other known breast pumps, or it requires the breast pump to simultaneously apply suction to the breast and increased pressure to the massaging membrane. The latter would require a more complex breast pump than is desired.
It is well known that suction applied to the breast in short pulses provides the most efficient milk expression. As known in the art, applying suction to the breast stimulates milk expression by mimicking the action of a baby. The flexible regions of known breast pumps can assist milk expression by providing a small massaging effect. However, the flexible regions move by a pressure differential across a thinned region of material and the massaging pressure is therefore minimal because it relies on stretching the material, which requires a lot of energy.
Known nipple shields have a constant wall thickness and are either too rigid due to thick walls, which inhibits massage, or too flexible due to thin walls, which do not provide enough protection for the mother and risk damage to the shield.